When a ring-twining or ring-spinning machine is brought to rest it is possible to observe the formation of curls or loops which are the more markedly present the greater is the degree of twist of the thread or twine. When the machine is started up again such curls may lead to difficulties since it cannot be guaranteed that the curls will be actually pulled out when the machine is started up. In addition, the thread or twine experiences a considerable loss of strength at the position of curling, which may lead to difficulties in further processing. The formation of curls may be ascribed to the fact that when the machine is brought to rest the machine itself comes to rest relatively quickly, because of the friction of the belt and of the bed and the action of the machine brakes, while the traveler, because of its low friction runs on for a longer time. In addition, the traveler also experiences additional acceleration due to the reaction forces produced in the thread by the twisting process. During normal operation, the traveler rotates at a speed corresponding to the speed of the spindle rotation less the velocity of the feed, i.e. in normal operation the traveler speed is always somewhat less than that of the spindle, but when the machine is shut off, the opposite situation occurs. The thread thus becomes slack and is able to curl up. Under favourable conditions it may also occur that the relation between the speeds of the spindle and traveler is maintained constant, so that the thread remains under tension until the machine comes to rest and no curls or only a negligible number are produced. But, in such cases, the traveler commences to move around the ring after the machine has come to rest because of reaction forces in the thread, so that yarn is unwound from the spool and the thread again becomes slack and able to form curls. Further, if during the shutting down of the machine, the speed of the spindle falls below a certain value, then the balloon of thread collapses so that a certain length of yarn becomes free and cannot be wound up again.
It is known (from French Patent Specification No. 1,339,833) to use a traveler brake in order to keep the thread under tension while the machine is being turned off. This traveler brake consists of a leaf spring which can be swivelled into the path of motion of the traveler. For this purpose the activating rod is designed as an axle extending in the longitudinal direction of the machine with one leaf spring attached to it for each twining-ring. When the machine is being turned off, the axle is rotated and the leaf springs are thus swivelled into their braking positions. In each of its rotations, the traveler strikes against the leaf spring and is braked by it. It is not, however, possible in this way to guarantee that the formation of curls will be prevented since the traveler is braked in the neighbourhood of the leaf spring only as long as it continues to rotate. When it comes to rest, after the machine has been turned off, at some particular point on the circumference of the twining ring then it may, because of the forces of reaction in the thread, move around the ring so that the thread becomes slack and curls up. In addition, it is disadvantageous that the traveler should be braked at a single point in its path of motion, since, in this case, a backward braking and thus an increase in the tension of the thread occurs at one point in its rotation, while in the rest of its path the traveler is able to turn freely without braking. The peaks of tension thus produced may lead to an impairment of the quality of the thread or even, under certain conditions, to breaking of the thread.
The basic object of the invention is therefore to design a traveler brake of the type described in the introduction which enables a uniform braking of the traveler throughout its motion and also the fixing of the traveler after it has come to rest.
This is achieved according to the invention in that the braking unit is designed to be ring-shaped and to extend over the whole path of motion of the traveler. By means of this design it is arranged that the traveler which has been brought to rest is fixed at whatever point on its rotation path it is situated. Thus the forces of reaction acting in the thread cannot move the traveler and the thread is held under continuous tension so that curls or loops can be eliminated with certainty. Since the braking unit extends in ring form over the whole path of motion of the traveler, the said traveler is braked uniformly over its whole rotation so that peaks of tension in the thread are avoided.
In order to improve the uniform action of the brake over the whole rotation further, it is convenient to provide the ring-shaped braking unit with a brake lining of an elastically flexible material on the faces opposite to the traveler. Foam rubber may be conveniently employed for this purpose. It is also possible to use soft rubber for this purpose.
An additional embodiment of the idea of the invention consists in that the braking unit is designed as a braking ring which can be moved up and down below the twining or spinning ring, the brake lining of said braking ring being able to be pressed against the traveler from below. Such a braking ring can be applied horizontally against the twining or spinning ring from below, preferably with the interposition of the above-mentioned brake lining, and thus makes possible a uniform braking effect over the whole path of rotation of the traveler.